Broach



F. J. LAPOINTE' BROACH Jan. 15, 1946.

Filed May 10, 1944 2 Sheets$heet 1 Jan. 15, 1946. F J, LAPO E 2392,8233

BROACHI Filed may I0, 1944 2 Sheets-Sheet 2 IN VENTOR.

Patented Jan. 15, 1946 BROACH Francis J. Lapointe, Ann Arbor, Mich.,assignor to American Broach & Machine 00., Ann Arbor, Mich., acorporation of Michigan Application May 10, 1944, Serial No. 534,848

8 Claims.

This invention relates to the art of broaching, and it is particularlyconcerned with a broach comprising a body with multiple cutters mountedthereon.

One object of the invention is to provide a novel and improved broachhaving a plurality of individual cutters mounted in a supporting base orbody.

Another object of the invention is to provide a broach comprising a bodyof relatively soft metal with a plurality of individual cutters ofwear-resisting metal mounted therein.

A further object of the invention is to provide a broach composed of ablock or base having a plurality of holes or sockets formed therein,spaced apart and arranged in rows and provided with a plurality ofindividual cutter elements secured rigidly in said holes or sockets butindividually removable for repair or replacement.

It is also an object of the invention to provide a broach comprising abody with individual cutters mounted therein in rows and spaced apartfrom each other, and with the cutters of one row sta gered with respectto those of an adjacent row so that the broach, as a whole, is adaptedto operate upon an entire continuous surface.

More specifically, the invention is concerned with a broach comprisin abody block of relatively soft metal, with a plurality of holes formedtherein in rows and spaced apart, and with slots cut in the marginalportions of the body at the ends of said rows, together with individualcutters set in said holes and in said slots and brazed therein, thecutters being arranged in staggered relation to insure operation upon anentire continuous surface and the spaces between the cutters serving aschip breakers in the operation of the broach.

Other objects and advantages of the invention will appear from thefollowing description taken in connection with the drawings in which:

Fig. 1 is a plan view of a broaching tool or unit embodying thisinvention. I

Fig. 2 is a side elevation of the same.

Fig. 3 is a transverse sectional view taken as indicated at line 33 onFig. 1.

Fig. 4 is a perspective view of an individual cutter before insertion inthe body of the broach.

Fig. 5 is a plan view of a modified form of broach unit'embodying theinvention.

Fig. 6 is a sectional view of the same, taken as indicated at line 65 onFig. 5.

Fig. 7 is a fragmentary plan view of a broach, showing a modifiedarrangement of the cutter bits to secure a shearing cut.

Fig. 8 is a fragmentary side elevation of the broach shown in Fig. '7.

While there is illustrated in the drawings and hereinafter described apreferred form of the invention, it is contemplated that variousmodifications may be made by thoseskilled in the art without departingfrom the spirit and scope of the appended claims.

In constructing broaches of high speed tool steel the practice has beento construct a nearly complete breaching tool and apply strips oftungsten carbide tool steel thereto by brazing such strips across theface of the tool and then grinding the final cutting edges therein. Thispractice was not only expensive but the heat gen-- erated in thegrinding would frequently cause surface cracks, and the brazing of theface pre-- sented a diflicult problem. Furthermore, with this continuoussurface of the harder material: it was necessary to grind in the notchesserving as; chip breakers and because of the hardness of the materialthis additional grinding was slow and expensive. The presentconstruction is designed to secure the advantages of modern high speedtool steels for the broaching work without the disadvantages heretoforeencountered in attempting to utilize this material in broaching tools.

As shown in the drawings, this construction comprises a body block orbase I having formed in it a plurality of holes or sockets 2 arranged inrows extending transversely of the block, that is, transversely of thedirection in which it is expected to move relatively to the work whenemployed in a breaching machine. As seen in Figs. 1, 2 and 3 the sockets2 are formed by first drilling round holes and then breaching them toform square-cornered sockets, by using a broach in which the width issomewhat less than the diameter of the drilled holes. Individual cutters3, shown as of square cross-section, are fitted snugly in the holes orsockets 2 and are rigidly secured therein by brazing. Preferably, at theends of the rows of holes 2 the block I is formed with slots 4 ofrectangular cross-section into which additional cutters 3 may be fittedsnugly and brazed in position, the slots 6 being formed in the marginalportions of the block I because they can be conveniently machined inthis form, whereas it is simpler to drill the round holes in theremaining areas of the block I and complete them by breaching asdescribed. Either form of socket will rigidly support one of theindividual cutters 3, the cutters in the slots 4 having cutting edgesterminating substantially flush with the sides of the block, as shown inFig. 1. Preferably, as shown in Fig. 2, the upper surface of the body orblock I is provided with transverse grooves or channels arranged just infront of each row of the cutters 3 to afiord ample space to accommodatethe chips removed by the cutting edges 3 in operation of the breach. Thebody block I may be secured to the supporting surface of thebroachingmachine in any suitable manner, as," for example, by means of boltsengag ing threaded holes 6 tapped in the rear face of the block, asindicated in Fig. 3.

Preferably, with a breaching tool of this type of construction, theindividual cutters 3 will be all of the same length, and the body I-will-be of uniform thickness, but may be mounted upon .:a tapered shim,indicated in dotted outline-at-l in Fig. 2. Thus, as each successiverowofthecutters 3 traverses the work an additional increment of material isremoved, until the required depth of .eut'has been effected. Inpractice,two or more unit breaches of the type illustrated hereinmay .be mountedin tandem -.on thetoolsupportof the .machine, .and'the. final breach.maybe supported on a shim of uniform thickness so, that its, cutterswill merely clean upanyunevenness in thesurface andprovide a finalfinishthereon. I

Breaches of this type are not confined to single- -surfaceoperation,.but may be mounteduponsuitable. supports. for simultaneouscutting on several ssurfaces, as,.fer example, ininternal work,eperating .-upon two, three .or four faces duringnthe .samestroke.

'As shown inthe drawings, theindividual .bits or...cutters3 are spacedapart in their rows by .distances slightly less than. the widthof eachcutter. Adjacent rows are staggered with respect to each other. so thatthe bits of one row are aligned with the spaces in the adjacent row andslightly overlap these spaces so that two rows of bits will completeoperation over the entire width of the surface. The spacing of theindividual bits automaticallyprovides the equivalent of the notcheswhich are usually cut into continuous cutting edges toserve as chipbreakers, so that the material cutfrom the workwillbe subdivided intosmall enough pieces to clear itself readily" from the'broaching' tool.This arrangement notponly saves the time and expense incident to grindinany chipbreakers'in a unitary or'continuous cutter, but avoids settingup any strains as between adjacent cutting edges, since'in the presentstructure the cutters are separatetool bitsconnected only by theirinsertion in the same base.

In making this type of breach the body or base block isdrilled andtheholes arebroached to form square-cornered sockets; then, if the unit isto be made so as to cut over its entire width, the marginal slots '4 arealso out, and may be breached so that they will fit. the tool bits? .60

within a few thousandths of an inch. Then all .the bits or cutters areinserted and secured by the brazing material shown at8, afterwhich thebreach is .ground'a'll ever .to'final size and the cuttingfaces of thetool bits are ground .and backed off on top to the proper shape. :Thiskeeps the cost of production comparatively low.

the event of injury or breakage of any of the cutting edges of theindividual bits the injured bit or cutter can be spot-heated to. thebrazing temperature and thenpushed out of the base so that a new bit canbeinserted .in .position' to replace it. When the entire breach has.been worn and re-groundtosuch an extent thatthe cutting 7 therein bybrazing.

breach can be heated to the low temperature required for loosening thebrazing, and all the bits can be removed and replaced with new bits,thus salvaging the body or base of the breach for use indefinitely.

Figs.'5 and 6 illustrate a modified construction in which the individualbits or cutters [3 are set into square holes or sockets l2 in the bodyblock H. Instead of being brazed in ,place they are secured byindividual set screws which are set obliquely into the block H adjacenteach socket l2 and are tapered or beveled at their inner ends forwedging contact with the bits Hi. This permits removal of any individualbit when required, and also allows replacement of all the bits whentheyare-worn out.

Fig.6 also shows a modified arrangement for amounting thebroach unit ona supporting member l5 of a breaching machine. The opposite end surfacesI6 and H of the body I l are oppositely inclined, .with-acorrespondingly shaped .bar i8 providingan inclined undercut surface 19engaging-the face lfi-and-a bar 20 havingits inclined face 2| in contactwith the face I! ofthe "breach body. An abutmentbar 22is :bolted inagroove. in the support, [.5 and the bar 20 is drawn intowedgingengagement between the bar-22 and the face I! when its holdingscrews 23 are tight- .-.ened.

iln-Figs. "Land .8 only a fragment of abase block Si is shown, but itmaybe understood that the entire block-will carry several transverselydisposed rows of cutter :bits 33. These bits-are shown set in-squareholes which are arranged in a stepped or ofi-set-ser-ies across thebaseblock 3 l, so that the row, asa whole, is inclincdto the directionuofscutting movement of the breach. .The cutting edges 33% of "the bits33 are. ground in alignment with each other which makes them .allslightly inclined to a line perpendicular to the vdirection of cuttingmovementand causes them -to operate with asheari-ngcut.

. It willbe understood. that, ordinarily, the-base or body block will.be made of relatively softv .or f-mild-steel, whilethe cutter bits will.be-special tool material, suchas the tungsten carbide tipped .bits nowavailable .-for us asalatherand pl tools. These bits are ready foruseupon grinding to; shape. and-adovgnot require hardening ertem-:;pe'ring. Thus; as compared withthe cost-of. a @unitary; solid: breachof high-speed steel thereiis ausavingin cost 10f material in making.thebody :of. ordinary .soft= steel, and therekis. a :saving 'of the:labor cost involvedinithehardening and tempering of .a unitary breach..zThetbody; is :merely "given a "normalizing 1 treatment, .or. may beleft inits original condition. "Furthermorathe risk of loss arising fromcracks, shrinkage, .warping and twisting ise'liminated and thespecial-equipment andfskill required for the hardening process maybe-dispensedwith.

- I claim as my invention:

1. A breaching tool-comprising=a body-block with a plurality-of roundholes spaced=at intervals 1 the-rein; said holes-having-angular groovesin their walls defining the corner portions-of square sockets, andiridividualcuttersof square cross section fitted in said sockets,respectively, and secured 2. A breaching-tool comprising a body blockwith aplurality of holes spaced apart therein, and individual cutterssecured respectively in said "holes of the block; said cutters'being'arranged in edges are: no longer .efficient,i'then'theentireflea-pluralityof -rows-extendingtransversely of the block andbeing spaced apart in said rows, the space between adjacent cutters ofany row being less than the width of the cutting edge of one cutter, andthe cutters of each row being disposed in staggered relation to thecutters of the adjacent row opposite the spaces of the latter, and withtheir cutting edges overlapping the paths of the cutters adjacent saidspaces respectively.

3. A broaching tool comprising a body block with a plurality of holesspaced apart therein and arranged in rows, each lateral marginal portionof the block having slots aligned with alternate rows of holes, andindividual cutters fitted and rigidly secured in said holes and slotsand with the cutters in the slots providing cutting edges whichterminate substantially flush with the sides of the block.

4. A broaching tool comprising a body block with a plurality of holesspaced apart therein and arranged in rows, each lateral marginal portionof the block having slots aligned with alternate rows of holes, andindividual cutters fitted and rigidly secured in said holes and slotsand with the cutters in the slots providing cutting edges whichterminate substantially flush with the sides of the block, the holes ofthe other rows and the cutters therein being disposed in sta geredrelation to the cutters of the adjacent rows.

5. A broaching tool comprising a body block with a plurality of roundholes extending in rows transversely of the block and spaced apart insaid rows, individual cutters of square cross-section fitted snugly insaid holes and brazed therein, said block having slots of squarecross-section cut in its lateral marginal portions, and individualcutters fitted in said slots and brazed therein in alignment with thecutters in said holes.

6. A surface broach comprising a body block with a plurality of holesspaced apart therein, individual cutters secured respectively in saidholes of the block, the cutting edges of all cutters being disposed atthe same distance from the bottom surface of the block, and a taperedshim positioned under the block to vary the effective height of thecutters progressively from one end of the block to the opposite end.

7. A broaching tool comprising a body block with a plurality of holesspaced apart therein, and individual cutters secured respectively insaid holes, said cutters being arranged in rows extending transverselyof the direction of cutting movement, and each cutter of a row beingoilset from the adjacent cutter in said direction of cutting movement,whereby the row as a whole is inclined to said direction.

8. A breaching tool as defined in claim 7, with the cutting edges of thecutters of each row aligned with each other and thus inclined to a lineperpendicular to the direction of cutting movement of the broach,whereby a shearing cut is made by said cutters.

FRANCIS J. LAPOINTE.

